Gear for Your Land Hermit Crab

Keeping a land hermit crab is simple. It has no special heating or lighting requirements, and little more than a proper terrarium, a suitable substrate, items to explore and play on, water and food dishes, and extra shells will be necessary to keep your crab. If you can, pick up these items at the same time you purchase your pet. Most pet shops carry a vast assortment of hermit crab supplies.

The best housing for land hermit crabs is a glass or plastic aq­uarium. Smaller crabs can live in a very large fishbowl, but larger crabs do best in a 10- to 15-gallon (38- to 57-L) aquarium, depending on the number of crabs you’re keeping. As many as five adult crabs can fit comfortably in a 10-gallon (38-L) aquarium, but keeping fewer crabs creates less mess in the terrarium.

Plastic carriers make excellent cages for one or two hermit crabs, and they can also serve as temporary housing for larger numbers. These carriers are easy to clean, durable, aesthetically pleasing, and often come with vented lids that are secure enough to hold large land hermits. Plastic carriers are also tall enough to allow you to add sufficient substrate and even a climbing branch or two, yet still give one or two crabs enough space to roam and exercise.

Whatever type of terrarium you use, put a lid on top so that your crab can’t climb out and so that you can maintain suitable humidity levels. A sheet of glass or plastic makes a fine lid, but covering the entire surface of the terrarium can cause condensation, which can be harmful and lead to the growth of fungi inside the terrarium. A sturdy lid with some ventilation is ideal for your land hermit.

If you keep a larger land hermit, fasten the terrarium lid in place with clamps or weigh it down to prevent your crab from escaping.

Your terrarium substrate can be anything from sand to aquarium gravel to potting soil. Calcium sand (rather than pure silica sand) is perhaps the best type of substrate for a land hermit crab—calcium is a vital nutrient that your crab can obtain by nibbling on a calcium-sand substrate. Many keepers also use crushed coral, coral rock, crushed clam and oyster shells, or limestone as a substrate.

Whatever substrate you use, keep a substrate depth of 1–3" (2.5–8 cm). Crabs often burrow in their substrate after molting, using it as both a hiding place and a place to stay moist. (Sand is especially well suited for this behavior.) If possible, try to keep the top of the sand relatively dry, but occasionally add water in the corners so that the sand near the bottom of the tank stays moist.

Land hermits like to climb, so provide different objects on which your crab can explore and move around. These items can include rocks, coral, driftwood, and ceramic ornaments. You should also provide a few hiding places in the tank for your crab to use during molting.

The distance from the tip of the highest point your crab can climb to in the terrarium to the lid should be more than twice the height of the crab and its shell. Land hermits are agile, curious animals that are prone to escape if given the opportunity to do so. If you keep multiple hermits, know that they can form bridges by climbing on each other’s backs, making it possible to reach points much higher up in the terrarium than they could reach on their own.

Land hermit crabs enjoy temperatures in the 75–80°F (24–27°C) range and can be comfortable without any additional heating. Avoid temperature extremes: at low temperatures—below 60°F (16°C)—the crabs become dormant and may die, while at high temperatures they try to burrow in their substrate or sit in their water bowl to cool off.

Don’t place your terrarium in direct sunlight or near radiators or air conditioners because this will rapidly change the temperature in your crab’s cage. If you do need to add a heat source to provide your crab with an optimal temperature, use a low-wattage heat lamp with a red or blue bulb so that the extra light doesn’t disturb the crab. Also install a thermometer in the terrarium and monitor the temperature daily to make sure you don’t overheat your crab.

Land hermit crabs need a relatively high humidity level in order to thrive. Try to keep the humidity in your enclosure at around 60–70%—you can keep the terrarium moist by misting your crab with moderately warm water several times a week. Never submerge your crab in water for any length of time. Hermits are land crabs and can drown when submerged in water.

The inside of the enclosure shouldn’t be damp all the time, and the bottom shouldn’t be moist all the way to the surface of the substrate. Try to maintain humidity so that the substrate is nearly dry at the top and turns moist closer to the bottom of the terrarium, as the crab burrows down into it. You can measure the humidity in your terrarium by purchasing a hygrometer (humidity gauge) and keeping it inside the terrarium.

Keep a shallow bowl of water in the terrarium so that your hermit crab can moisten its gills on a regular basis and add some water to its shell for trips to dry areas in the enclosure. Because your crab will climb inside the water bowl to clean out its shell, the bowl should be easy for the crab to enter and leave—a crab can drown if it gets stuck in its water dish. The bowl should also be difficult to tip over, and the bottom shouldn’t be slippery.

Although hermits are marine crabs, many can thrive with clean, fresh water as well as salt water. However, there are some land hermits from areas with little fresh water that can live only on salt water. It may be best for your crab (especially if you’re uncertain of its species and whether it can tolerate fresh water) if you include one dish of fresh water and one of salt water. A solution of 1 ounce (28 g) of noniodized table salt or commercial sea salt in 1 quart (1 L) of water should be an acceptable mix.

If your crab can survive on fresh water, or if you have to make your own salt water at home, use bottled water instead of tap water if you have any doubts about your water’s purity. This will prevent chlorine and other chemicals from harming your crab.

Maintenance of your crab’s enclosure is not difficult. Once every few days, check the terrarium for dirt, waste matter, and bits of food, and remove it. You can also rinse your crab and its shell in clean water once a week so that food residue doesn’t get trapped inside the shell, there is some water for the crab’s gills, and the shell stays clean and bright.

Your terrarium will need a thorough cleaning at least once a month. If you’re using gravel as a substrate, remove all of it, rinse it well without soap (which is toxic to your crab), and let it dry before returning it to the tank. If you’re using sand as a substrate, replace it once a month to prevent feces and uneaten food from building up in the cage.